Previous studies in neurologically intact subjects have shown that motor coordination can be described by task-dependent combinations of a few muscle synergies, defined here as fixed pattern activation across set muscles. Arm function severely impaired stroke survivors is characterized stereotypical postural and movement patterns involving the shoulder elbow. Accordingly, we hypothesized synergy composition altered survivors. Using an isometric force matching protocol, examined spatial elbow...

This study presents the results of a novel paradigm for characterizing abnormal coordination in subjects with hemiparesis. Subjects generated maximum voluntary torques (MVTs) isometrically four randomly ordered blocks consisting elbow flexion/extension, shoulder abduction/adduction, and external/internal rotation. A 6–degree-of-freedom (DOF) load cell was used to measure secondary DOFs at shoulder, as well torque direction subject attempting maximize. allowed characterization multijoint...

Abstract The ability to extend the elbow following stroke depends on magnitude and direction of torques acting at shoulder. mechanisms underlying this link remain unclear. purpose study was evaluate whether effects shoulder loading function were related weakness or its distribution in paretic limb. Ten subjects with longstanding hemiparesis performed movements arm either passively supported against gravity by an air bearing, activation muscles. Isometric maximum voluntary measured using a...

Previous studies using advanced matrix factorization techniques have shown that the coordination of human voluntary limb movements may be accomplished combinations a small number intermuscular patterns, or muscle synergies. However, potential use synergies for isometric force generation has been evaluated mostly correlational methods. The results such suggest fixed relationships between activations pairs muscles are relatively rare. There is also emerging evidence nervous system uses...

Previous studies indicate that motor coordination may be achieved by assembling task-dependent combinations of a few muscle synergies, defined here as fixed patterns activation across set muscles. Our recent study severely impaired chronic stroke survivors showed some synergies underlying isometric force generation at the hand are altered in affected arm. However, whether similar alterations evident with lesser impairment remains unclear. Accordingly, we examined spatial elbow and shoulder...

Clinically, upper-limb discoordination after stroke is evident in the form of stereotypic movement patterns that reflect a loss independent joint control. These abnormalities, conjunction with our recent quantitative findings under isometric conditions, provide evidence for an impaired capacity to generate certain muscle coactivation limb. In this article, we examine parallels exist between coordination disturbances observed and conditions. Our results suggest may largely represent...

Abstract Unlike individuals with mild stroke, severe stroke are constrained to stereotypical movement patterns attributed abnormal coupling of shoulder abductors elbow flexors, and adductors extensors. Whether muscle coactivation associated joint torque can be changed in this population is important determine given that it bears on the development effective rehabilitation interventions. Eight subjects participated a protocol was designed reduce elbow/shoulder by training them generate...

This paper describes the design and operation of multi-axis cartesian-based arm rehabilitation machine (MACARM), a new cable (wire) robot for upper limb rehabilitation. The prototype configuration is comprised an array 8 motors mounted at corners cubic support frame that provides, via cables, 6 degree freedom (DOF) control centrally located end-effector. A DOF load cell on end-effector provides force measurement. Given its relatively simple architecture, MACARM may provide attractive...

We examined spatiotemporal abnormalities in the flexor reflex response impaired upper extremity of hemiparetic subjects. Electrical stimulation was used to elicit flexion reflexes both extremities 8 brain-injured and 6 control Electromyograms (EMGs) were recorded from 12 arm muscles, forces moments at wrist with a load cell, converted shoulder elbow torques. found that onset torque EMG delayed delays greater than elbow. The normal consisted flexion, extension, adduction. In contrast, limb...

The generation of isometric force at the hand can be mediated by activating a few motor modules. Stroke induces alterations in modules underlying steady-state human upper extremity (UE). However, how altered impact task performance (force production) remains unclear as stroke survivors develop and converge to three-dimensional (3D) target force. Thus, we tested whether stroke-specific would activated from onset also examined induce changes representation. During 3D development,...

External support of the arm against gravity has a beneficial impact on reaching movements performed by moderately and severely impaired stroke survivors. Provision scalable compensation may therefore be an important component robot-based upper limb rehabilitation. This study reports development initial evaluation gravity-compensated training environment based haptic capabilities MACARM cable robot. The feasibility end-point force for torques at shoulder elbow is evaluated in vertical plane....

This paper describes the technical evaluation of Multi-Axis Cartesian-based Arm Rehabilitation Machine (MACARM), a cable robot for upper limb rehabilitation. The MACARM was evaluated static and dynamic positional accuracy, force performance, speed work volume. Results indicate errors smaller than 1% movement magnitude, indicating stable performance throughout tested range. In addition, demonstrated favorable path repeatability, critical element ldquoteach playrdquo approaches to robotic...

Despite the fundamental importance of muscle coordination in daily life, it is currently unclear how adapts when musculoskeletal system perturbed. In this study, we quantified impact selective weakness on several metrics coordination. Seven healthy subjects performed 2D and 3D isometric force target matches, while electromyographic (EMG) signals were recorded from 13 elbow shoulder muscles. Subsequently, was induced by a motor point block brachialis muscle. Postblock repeated generation...

The purpose of this study was to quantify the degree weakness and possible existence abnormal torque synergies in upper limb stroke subjects. Subjects produced static elbow shoulder torques which were measured using a 6 freedom (DOF) load cell for two separate protocols: uncontrolled maximum generation (UMTG), single specified joint (either or shoulder); controlled (CMTG) required subject produce maximum-submaximum elbow/shoulder combinations. Impaired arms exhibit all physiological degrees...

The purpose of this study was to explore the relationship between abnormal static torque synergies and disturbances planar arm movements in stroke subjects (n=3). Abnormal (e.g. coupling shoulder abduction-external rotation elbow flexion torques) were identified impaired all three using 6 degree freedom load cell measurements. As a result, ability produce extension abduction torques simultaneously severely compromised. Based on comparisons actively passively supported movements, similar...

Analyses of hand movement planar trajectories in paretic and contralateral arms hemiparetic stroke patients indicate that there are disturbances all phases limb motion, including the initial direction, mid-course trajectory, terminal deceleration phase associated with termination. kinematic kinetic characteristics concurrent electromyograms suggest trajectory mediated by several deficits. These include disruption spatial coordinate frameworks specifying motion loss internal models mechanical...

Flexion withdrawal responses in the impaired/unimpaired upper limbs of hemiparetic stroke subjects were studied to determine relationship between cutaneous afferent input and abnormal muscle synergies. A mildly noxious electrical stimulus was applied index finger while concurrently measuring relevant EMG joint torque responses. The reflex response impaired arm significantly altered. onsets delayed at both shoulder elbow across all along with reversals two three torques (adduction-abduction...